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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#pragma once
#include "base/compiler_specific.h"
#include "ipc/ipc_channel_handle.h"
#include "ipc/ipc_message.h"
namespace IPC {
// See
// for overview of IPC in Chromium.
// Channels are implemented using named pipes on Windows, and
// socket pairs (or in some special cases unix domain sockets) on POSIX.
// On Windows we access pipes in various processes by name.
// On POSIX we pass file descriptors to child processes and assign names to them
// in a lookup table.
// In general on POSIX we do not use unix domain sockets due to security
// concerns and the fact that they can leave garbage around the file system
// (MacOS does not support abstract named unix domain sockets).
// You can use unix domain sockets if you like on POSIX by constructing the
// the channel with the mode set to one of the NAMED modes. NAMED modes are
// currently used by automation and service processes.
class Channel : public Message::Sender {
// Security tests need access to the pipe handle.
friend class ChannelTest;
// Implemented by consumers of a Channel to receive messages.
class Listener {
virtual ~Listener() {}
// Called when a message is received. Returns true iff the message was
// handled.
virtual bool OnMessageReceived(const Message& message) = 0;
// Called when the channel is connected and we have received the internal
// Hello message from the peer.
virtual void OnChannelConnected(int32 peer_pid) {}
// Called when an error is detected that causes the channel to close.
// This method is not called when a channel is closed normally.
virtual void OnChannelError() {}
#if defined(OS_POSIX)
// Called on the server side when a channel that listens for connections
// denies an attempt to connect.
virtual void OnChannelDenied() {}
// Called on the server side when a channel that listens for connections
// has an error that causes the listening channel to close.
virtual void OnChannelListenError() {}
#endif // OS_POSIX
// Flags to test modes
enum ModeFlags {
#if defined(OS_POSIX)
MODE_OPEN_ACCESS_FLAG = 0x8, // Don't restrict access based on client UID.
// Some Standard Modes
enum Mode {
// Channels on Windows are named by default and accessible from other
// processes. On POSIX channels are anonymous by default and not accessible
// from other processes. Named channels work via named unix domain sockets.
// On Windows MODE_NAMED_SERVER is equivalent to MODE_SERVER and
// MODE_NAMED_CLIENT is equivalent to MODE_CLIENT.
#if defined(OS_POSIX)
// An "open" named server accepts connections from ANY client.
// The caller must then implement their own access-control based on the
// client process' user Id.
enum {
// The maximum message size in bytes. Attempting to receive a
// message of this size or bigger results in a channel error.
kMaximumMessageSize = 128 * 1024 * 1024,
// Ammount of data to read at once from the pipe.
kReadBufferSize = 4 * 1024
// Initialize a Channel.
// |channel_handle| identifies the communication Channel. For POSIX, if
// the file descriptor in the channel handle is != -1, the channel takes
// ownership of the file descriptor and will close it appropriately, otherwise
// it will create a new descriptor internally.
// |mode| specifies whether this Channel is to operate in server mode or
// client mode. In server mode, the Channel is responsible for setting up the
// IPC object, whereas in client mode, the Channel merely connects to the
// already established IPC object.
// |listener| receives a callback on the current thread for each newly
// received message.
Channel(const IPC::ChannelHandle &channel_handle, Mode mode,
Listener* listener);
virtual ~Channel();
// Connect the pipe. On the server side, this will initiate
// waiting for connections. On the client, it attempts to
// connect to a pre-existing pipe. Note, calling Connect()
// will not block the calling thread and may complete
// asynchronously.
bool Connect() WARN_UNUSED_RESULT;
// Close this Channel explicitly. May be called multiple times.
// On POSIX calling close on an IPC channel that listens for connections will
// cause it to close any accepted connections, and it will stop listening for
// new connections. If you just want to close the currently accepted
// connection and listen for new ones, use ResetToAcceptingConnectionState.
void Close();
// Modify the Channel's listener.
void set_listener(Listener* listener);
// Send a message over the Channel to the listener on the other end.
// |message| must be allocated using operator new. This object will be
// deleted once the contents of the Message have been sent.
virtual bool Send(Message* message);
#if defined(OS_POSIX) && !defined(OS_NACL)
// On POSIX an IPC::Channel wraps a socketpair(), this method returns the
// FD # for the client end of the socket.
// This method may only be called on the server side of a channel.
int GetClientFileDescriptor() const;
// On POSIX an IPC::Channel can either wrap an established socket, or it
// can wrap a socket that is listening for connections. Currently an
// IPC::Channel that listens for connections can only accept one connection
// at a time.
// Returns true if the channel supports listening for connections.
bool AcceptsConnections() const;
// Returns true if the channel supports listening for connections and is
// currently connected.
bool HasAcceptedConnection() const;
// Returns true if the peer process' effective user id can be determined, in
// which case the supplied client_euid is updated with it.
bool GetClientEuid(uid_t* client_euid) const;
// Closes any currently connected socket, and returns to a listening state
// for more connections.
void ResetToAcceptingConnectionState();
#endif // defined(OS_POSIX) && !defined(OS_NACL)
// Used in Chrome by the TestSink to provide a dummy channel implementation
// for testing. TestSink overrides the "interesting" functions in Channel so
// no actual implementation is needed. This will cause un-overridden calls to
// segfault. Do not use outside of test code!
Channel() : channel_impl_(0) { }
// PIMPL to which all channel calls are delegated.
class ChannelImpl;
ChannelImpl *channel_impl_;
// The Hello message is internal to the Channel class. It is sent
// by the peer when the channel is connected. The message contains
// just the process id (pid). The message has a special routing_id
enum {
HELLO_MESSAGE_TYPE = kuint16max // Maximum value of message type (uint16),
// to avoid conflicting with normal
// message types, which are enumeration
// constants starting from 0.
} // namespace IPC
#endif // IPC_IPC_CHANNEL_H_